The present invention relates to the field of coatings and surface treatments for objects, which objects may be fabricated from metals, polymers, ceramics, glass, or composites thereof.
It is often desirable to improve the durability, wear resistance, surface hardness, and so on, of objects, such as gears, bearings, and other mechanical components, without having to resort to a change in the basic material from which the object is generally formed or fabricated. Such a change may often result in the unnecessary usage of expensive, rare, or difficult-to-work-with materials, and increased manufacturing effort and cost necessary to produce the particular object.
Wear of the surface of an object can be expressed in terms of three different processes which can occur. A surface can be damaged, such as by striking or impingement by a sharper or harder object, such that indentations, pits or holes are produced which are relatively large in comparison to the contour or texture of the surface. The surface can lose material as exposed portions of the particles making up the surface are broken, or entire particles are pulled away from the surface. Further, the particles which make up the interface between one layer and another can become separated, such that the layers become separated.
In order to improve the wear characteristics of a surface, the three described processes must be slowed. Damage to the surface is reduced by increasing hardness. Breakage and pull-away of particles from a surface is reduced by lubrication, or by increasing the surface lubricity of the object. Interface separation is reduced by using composite structures to alter the electrostatic characteristics of the materials making up the interface.
The performance characteristics of a mechanical component can often be improved, or changed to have specific desired characteristics, through various treatments of the surface of the object, for example, by various combinations of heat treatment, possibly combined with working of the surface of the object. The performance characteristics of the object may also be affected by the addition of layers of other materials, such as by cladding or coating. Improving the surface hardness and wear resistance of certain mechanical components, such as gears or bearings, or increasing the edge retention or abrasiveness of a surface, such as for a cutting or drilling tool, through the coating or plating of the object with a layer of metal, or a layer of material including a metal, is known in the prior art.
One material which has proven to be a useful anti-friction material is particulate diamond. U.S. Pat. No. 5,158,695 to Yaschenko et al., for example, shows the use of particulate diamond material as an anti-friction material.
The Yaschenko patent describes a material which was stated to be used in machine components which are subjected to wear due to friction. The Yaschenko reference describes using bars made of antifriction material (structures fabricated from mainly sintered copper-based intermetallides with zinc and tin, with dispersed diamond powder) for rubbing-in. The Yaschenko reference also describes uses of the new antifriction material to make substantially wearless sliding bearings and bushingless internal combustion engines.
The size of the particulate diamond material employed in the Yaschenko patent was 0.1 micrometer. The particulate diamond material concentrations employed ranged from 5.0 to 50 percent of the overall mass of the antifriction material. The Yaschenko patent then compared the use of the particulate diamond material as an anti-friction additive material to molybdenum disulfide, graphite and molybdenum disulfide, and copper-tin-zinc-graphite-cubic boron nitride. In Yaschenko, it was proposed that the use of additive material containing the diamond particulate powder in a range of 5.0 to 50 percent mass resulted in a higher scoring strength than the additive materials without the diamond particulate. Furthermore, it was also concluded that diamond powder having a grain size less than 0. 1 micrometer was preferred in order to maintain reinforcement of the metal surface without obtaining an abrasiveness.
Such prior usage of diamond particulate material has, however, not achieved a significant improvement in the tribological, or anti-friction, properties between two surfaces because of the weak physical bond between the rubbing bar materials and the treated surface. The Yaschenko anti-friction material contains a soft metal, such as copper or tin, as the lubricating agent and the diamond particles are used as a reinforcing agent. Using the soft metal itself as the lubricating agent improves the friction process; the diamond reinforcing agent, in the material of the Yaschenko reference, simply improves the strength and life of the lubricating agent and does not directly act as a lubricating agent. In the prior art method of Yaschenko, a method is disclosed for increasing the lubricity of two sliding surfaces by placing diamond particle into a solid antifriction material, which is then applied, as a treatment (rubbing-in) bar or as a bushing or the like. In such a utilization, the diamond particles do not increase the lubricity of the relatively sliding surfaces. The diamond particles only assist in increasing the time that the lubricating agent (copper, tin, etc.) stays between the relatively sliding surfaces. The diamond particles do not work as a lubricating agent, since the particles do not have contact with the sliding surfaces, due to the presence of the solid lubricating agent.
Such prior art methods will not reduce the coefficient of friction of the relatively sliding surfaces. Further, such solid antifriction materials can have limited applications.
It is desirable to provide a treatment for surfaces which are configured for relative sliding movement, in which the material which is utilized for providing antifriction properties will achieve a good bonding or adherence to at least one of the relatively sliding surfaces.
This and other objects of the present invention will become apparent in light of the present Specification, Claims, and Figures.